In general we can't iterate through all MetadataSource implementations, because get_next_block is allowed to return None if metadata is not yet available, but might become available in time for rendering.
Allowing iteration through a MetadataSourceIter would be fine though, and would make using rendering items in scripts where we know we're always going to have a MetadataSourceIter a bit nicer.
In general we can't iterate through all
MetadataSourceimplementations, becauseget_next_blockis allowed to returnNoneif metadata is not yet available, but might become available in time for rendering.Allowing iteration through a
MetadataSourceIterwould be fine though, and would make using rendering items in scripts where we know we're always going to have aMetadataSourceItera bit nicer.